考虑局部屈曲的薄壁铝合金压弯构件破坏机理及承载力计算方法

The aluminum alloy structure component usually uses thin-walled cross section to increase its utilization. At the same time, the Young's modulus of aluminum alloy is only 1/3 of that of steel, thus aluminum alloy structural member is more vulnerable to local buckling. Although current design methods for the yielding and global buckling strength of an aluminum alloy member under the combination of axial load and bending moment considered influence of the local buckling, three points should be studied further: (1) The effective section for considering the local buckling effects was only determined by the width to thickness ratio of the plate when calculating the yielding strength of the member under the combination of axial load and bending moment. Comparison between the compression stress and the local buckling stress was not carried out to decide whether the effective section should be used or not; (2) When calculating the global buckling strength, the gross section was used to calculate the axial strength without considering local buckling. The effective section was used to calculate the bending moment strength while magnitude of the compression stress in the section was not considered; (3) The effective thickness method only considered the reduction of the strength of the plate encountered local buckling. The changes of the cross-section shape due to local buckling should also be included when calculating the yielding and buckling strength of the column under the combination of axial force and bending moment. This proposal is aimed to build equations for calculating the effective thickness of a local buckled plate considering the magnitude of compression stress. The influence of the cross-section shape variation due to local buckling to yielding and global buckling strength is also included. Research results of this project may help to increase the precision of the design equations for aluminum alloy structure.

铝合金构件多采用薄壁结构以提高材料利用率；且铝合金的弹性模量仅为钢材的1/3，构件易发生局部屈曲。现有铝合金压弯构件强度和稳定承载力计算方法虽考虑了局部屈曲的影响，但仍存在不足：(1) 计算强度破坏承载力时，仅根据板件受压状态和板件的宽厚比确定有效截面来考虑局部屈曲影响，并未考虑板件压应力与局部屈曲应力之间的大小关系； (2) 计算稳定破坏承载力时，轴力项中截面面积采用原截面，未考虑局部屈曲的影响；弯矩项中截面抵抗矩虽采用有效截面，但计算有效截面未考虑板件压应力大小；(3) 有效截面计算时的有效厚度法仅根据局部屈曲应力与屈服强度的关系对板件厚度进行折减，未考虑局部屈曲后板件位置和截面形状改变对承载力的影响。通过本项目研究，建立考虑板件压应力大小的压弯构件有效截面和承载力计算方法，并进一步考虑板件局部屈曲后截面形状改变对承载力的影响，使铝合金结构的设计更科学合理。

进行了复杂薄壁截面铝合金轴压构件受力性能试验研究：对复杂薄壁截面铝合金试件进行轴压试验，研究了该类截面构件轴压作用下局部屈曲及局部与整体耦合屈曲的性能。试验结果表明：各国规范均保守估计了复杂截面铝合金构件的屈曲承载力，而直接强度法相比各国规范可更精确地计算复杂截面铝合金轴压试件的屈曲承载力。.研究了考虑局部屈曲对构件整体稳定承载力的影响，提出了铝合金构件局部屈曲与整体屈曲耦合破坏下的承载力计算方法，并基于多重屈曲耦合理论，建立了构件发生强度破坏和稳定破坏时其承载力的计算分析方法，使现有设计公式更加合理。提出了确定有效截面时所考虑的压应力与板件局部屈曲应力之间的大小关系；分析了板件的应力梯度、支撑条件、加劲肋设置和板件缺陷类型等对确定板件局部屈曲应力的影响，根据压应力与板件局部屈曲应力的大小关系确定是否采用有效截面，并提出了相应的计算方法，弥补了现有设计方法仅根据板件受压及宽厚比大小确定有效截面的不足。.对上述问题的研究，提出了铝合金结构相应的分析模型和分析方法，建立了更准确的铝合金结构设计理论，具有重要的理论和社会价值。随着铝合金结构设计分析理论的完善，铝合金结构在建筑多高层结构、大跨空间建筑，城市交通人行天桥结构中的应用前景，将更加广阔。